Typically the openings in a beer can end or a carbonated beverage can end include one large opening for dispensing the enclosed liquid and a smaller opening for allowing the entrance of atmospheric air. The openings are filled with metal buttons which are hinged to the can end. The inside periphery of the buttons needs to be sealed preferably with a plastics material such as plastisol.
U.S. Pat. No. 4,005,960 which issued Feb. 1, 1977 for an apparatus for applying plastics to planar surfaces is representative of the prior art. In that patent, a can end is positioned beneath a pair of dispensing nozzles which were aligned with the openings in the can end. The dispensing nozzles are sized and positioned to deliver a sealing plastics material, such as plastisol, downward onto and around the openings within the can end.